The backing from the Edinburgh-based fund manager came a day after the Takeover Panel made a pivotal decision to raise no “concert party” objections to the three buyers of a 13.4pc voting stake from Rosan Roeslani’s Recapital fund. All three are expected to back the board.

The coal miner’s board needs just over 90m of the 181m votable shares in issue to rebuff Mr Rothschild at Thursday’s extraordinary meeting – assuming all shares are voted.

Adding Standard Life’s stake of around 4m shares to the 24.2m sold by Recapital and the 54m that can be jointly voted by Indonesia’s Bakrie family and Bumi chairman Samin Tan brings the board’s support to more than 82m shares.

However, it is also counting on the backing of two hedge fund managers Orchard Capital and Route One, which hold about 4.6m shares between them. That brings the board’s total to 86.8m – a formidable bloc given that all shareholders are unlikely to vote. Mr Rothschild, who so far has 35pc-40pc shareholder support, has already claimed to the Takeover Panel that Orchard Capital and Route One have links to the Bakries.

Mr Rothschild had been hopeful of winning over Standard Life. But the group’s head of equities David Cumming said yesterday: “After careful consideration of the resolutions we believe the restructured Bumi board has the best prospects of exiting the Bakrie relationship and maximising long term value for the remaining shareholders.” He said he would “support the Bumi board” but called for a strengthened executive team.

Mr Rothschild said it was Mr Cumming’s “initial support of the EGM concept” that led him to call the meeting and that both of them agreed the board and management “needs to be restructured”.

In a veiled criticism of the Panel, Mr Rothschild added the vote had now come down to “the Takeover Panel’s decision to admit new shareholders at the 11th hour”. He is thought to have been stunned that all three buyers of the Recapital stake – Avenue Luxembourg, Argyle Street Management, and the Flaming Luck vehicle of Indonesia’s Tanoesoedibjo family – were cleared of not being in concert with the Bakries.

A media company owned by Mr Tanoesoedibjo recently tried to buy media assets from the Bakries, who were planning to use the proceeds to buy back Bumi Resources, in which London-listed Bumi holds a 29pc stake.

A source close to the Panel stressed it would have done its due diligence on the buyers. “The Takeover Panel doesn’t shoot from the hip,” the source said.

Richard Knights, a Liberum analyst said: “I think the Panel would have made the decision on the basis of the information they had. They don’t take sides.”